Hi everybody,

Please take a little time for my rather long story, but consider the fact that I' am struggling with this matter for more than a year.
I've bought a Audi TT 1.8 Turbo, quattro, 225 HP with APX engine, from the year 2000 and soon I have discovered that the turbine (turbocharger) is broken - was throwing oil in the exhaust system and the effect was a black smoke.
I've changed the turbine, then because VAG-COM reported a error I've changed the Lambda oxygen sensor everything was OK in respect with the VAG-COM, or at least I got no more errors.

Then I have noticed ( I don't remember if this happend before I changed the turbine) this strange behaviour: whenever I relase too suddenly the throttle pedal I hear a noise in the air filter area (some kind of rattling) and the engine rpm drop dangerously to a 400 - 600 rpm. Sometimes in slow speed corners the engine stops.

For this I have changed the throttle body with a new one, after many calibrations and cleanings - no difference.

Recently I have changed the debitmeter with a new one and everything got crazy. First the car worked almost as before - with a small lack of power when I begun to press the acceleration pedal.
When I stoped after few kilometers I received the error:


Control Module Part Number:
Component and/or Version: 1.8L R4/5VT 0001
Software Coding: 05710
Work Shop Code: WSC 00000
1 Fault Found:
16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-00 - - - Intermittent

Then I cleared this error, made another few kilometers and I got:


Control Module Part Number:
Component and/or Version: 1.8L R4/5VT 0001
Software Coding: 05710
Work Shop Code: WSC 00000
1 Fault Found:
16514 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit
P0130 - 35-10 - - - Intermittent

I cleared also this error, I have callibrated the throttle body and I got again the Lambda error.
I have cleared again the Lambda error and then the car became not stable when I started it. It didn't start at the first few tries, I got a huge rpm variation, I got explosions in the exhaust etc...

I had to disconnect the debitmeter (pulled of the power cable) and the car worked different in the sense that it was the first time I didn't experienced rpm drops, although the noise in the air filter area was still persistent. But, I couldn't go over 3500 rpm - it was clear that this was not the fix.

In the next morning I have connected the debitmeter back, got difficulties when I tried to start the engine but I have hepled the engine to start by pressing hard the throttle pedal. Whenever the engine passes the first phase, with the acceleration help it goes to a "normal" behaviour.

Because I got again the Lambda error I have put it out and clean it, although it was allready clean. From then on I received no more Lambda errors.

I have drove the car, with a difficult start, but then it worked fine, on the highway with 130 - 160 km/h. When I got off the highway, after couple of kilometers with 40 - 100 km/h, the ESP warning on bord lighted up. I have stoped and I have seen that I had the new error:

Control Module Part Number:
Component and/or Version: 1.8L R4/5VT 0001
Software Coding: 05710
Work Shop Code: WSC 00000
1 Fault Found:
16487 - Mass Air
Flow Sensor (G70): Signal too High
P0103 - 35-10 - - - Intermittent

Even though I have cleared the error in the next 100 km it appeard again a couple of times everytime announced by the ESP on bord.

I stoped, cleared the error, didn't start the car for few days then I made around 300 KM - normal rode and highway. I had dificulties to start the car but then it worked almost like before I changed the debitmeter and ... I got no more errors! The next day, after a difficult start I drove around 10 km but again no errors.

What I have noticed and I believe it is important is that whenever I have dificulties to start the car, in the "001" Measuring Blocks field in VAG-COM I got at "HOS2 Control" a constant "25%" value. Anytime else I got a constant variation from -7% to +10%.

Well, that's the story... If it not clear please indicate me what else should I do and what other data may I offer you. Maybe based on your experience you can help me clarify:

- why the car is producing a rattling noise while decelerating in the air filter area? I believe that it is relared with the "cut-off" valve but how can I decide it is broken, what experiments should I make, what data in VAG-COM should I follow?

- why is the rpm dropping when I take the foot off the pedal?

- is the new debitmeter broken, or is the old one but in such manner that it hides some of the car's vices?

- what do you think I should do to solve the problem or make it clear?

- should I post this also on General Tech area for better chances for anwers?

 

Ok well first to start off, Welcome to the Forum. Let me see if I can shed some light on your situation. First of all you either have a AMU or BEA engine code. The 225 only came in either of those two. BEA being the latter and with VVT. So you have a AMU engine code just like mine. Unless its European but I still think the engine code is the same. Anyways going back on subject your Mass Air Flow sensor sounds like it is going out. I would take it out and replace it with a new one. That is going to take care of most of your problems (I think). The rattling, well that could be a broken DV when you release the throttle air is trying to escape and becasue of the broken valve inside it will rattle. If not take the whole intake off(yes down to the turbo) and shake it too see if anything rattles. If so replace whatever it is. My best guess is to go get a new DV and a Mass Air Flow Sensor, replace those two, clear all codes and drive normaly for awhile. Let me know if this helps.

 

Thank you for your fast response!

1. The engine code is APX - indeed the car is European.
2. I have just changed the MAF with a new one, with the old one I received no errors. All the errorrs occured after calibration. For two days I received no more errors.
3. Does DV comes from Diverter Valve? It is the valve that directs the air flow in the turbocharger or not?
4. From 2+3: Is it possible that only because of the DV to have both the noise and the rpm drops?
Does anyone experienced such a noise in the air filter area and can confirm that is the DV responsible for this?

 

Yes the Divertion Valve is what it is called. You can buy them from many differnt places. I know that www.thettshop.com is a european based company and should be able to hook you up. Also you can look into aftermarket pieces, high performance divertion valves. I would highly recomend that you change this as well. Check all your hoses to your intercoolers to make sure that they didnt come off, and get a boost gauge. It will help you now and in the future if you ever do have problems with your TT again.

"16486 - Mass Air Flow Sensor (G70): Signal too Low"
"16487- Mass Air Flow Sensor (G70): Signal too High"
Those are the keys to that your mass air flow sensor was going out.

"16514 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit"
Could of been the indicator that your DV is bad, it may show up again. Or your O2 sensor could of just gone out, it happens. But I would replace the DV ASAP. The car will run like **** between shifts, and when you let off the accelerator too quickly.

 

Hello,

Well I have finally replace the DV. The resoults are good: the noise dissapeared or atleast is hardly noticeable and the rpm drops are now smaller and rarely appear.
But... to be able to use the car untill I got the DV I have put back the old MAF and I have returned the new one (I descriebed the problems related with the new MAF in my first post). Since then I experience a engine power loss. I am still hearing the turbo but the car lack's power.
Please see the VAG-COM log file in which I have also generated a graph: http://www.yousendit.com/download/WF...YTIrV3cwTVE9PQ
What I suppose is that there is a problem with the turbo pressure because the actual pressure (@Intercooler) (with the red color), is allways less than requested presure - yellow. In fact the pressure only incerases if I press at once and very hard the gas pedeal. If I press it gredualy nothing happens. Is this normal? With blue are the rpm. With green are the verry slow values recorded by the MAF. What do you think about these measurements?

 

Are you getting any check engine lights now? Also check to see if you have any boost leaks, vwvortex has a good writeup for this as well as audiworld.com. That could be your problem, or at least part of one.

Also do you have a boost gauge, your car may be in "limp" mode, to clear this disconnect the positive from the battery wait 15-20min then reconnect it back up, (have to unlock everything, radio, windows etc..) and drive it around and see if that helps. Also if you dont have a boost gauge now is a great time to go and get one!

 

I ain't got no error code in VAG-COM, hence I don't believe that the car is in limp mode.

"A good writeup for checking boost leaks"? Do you have a link for this?

Boost gauge? Hmm I don't think it will show me more data than the VAG-COM. This ain't seems to be a priority right now.